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Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds one useful behavioral detail: the value is a cached snapshot from the last synchronization, not a live query. It does not say what happens when an account has never synced or how stale the snapshot may be, so the added context is real but limited.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is one compact sentence with no filler, and the account scope and provenance are front-loaded. It is appropriately sized for a one-parameter lookup, though the terse phrasing leaves no room for the missing usage and parameter guidance.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter read tool with no output schema, the description conveys the core return concept (current balance) and notes its freshness. It omits what the balance value looks like, currency handling, and the meaning or source of conta_id, so an agent has enough to attempt the call but not enough to use it confidently.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the single required parameter conta_id is undocumented in both the schema and the description. The description does not say what a conta_id is, where to obtain one, or whether it must come from listar_contas. With low coverage, the description should compensate, and it does not.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific resource and scope: the current balance of one account. It also states provenance ('as the bank informed on last sync'), which separates it from transaction or invoice siblings. It stops short of naming which sibling to use instead, so it is clear but not fully differentiated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit when-to-use guidance and no mention of alternatives such as listar_contas or transacoes. An agent can infer this is a point lookup for one account, but nothing in the text confirms that or states when another tool should be preferred.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.